The invention relates generally to drain boards and more particularly to a drain board for applying a liquid film to a web of textile material.
These types of devices are used, for example, in the dyeing of webs of carpet. The liquid dye is applied to the drain board, whether it be by applying it with a doctor blade or by pouring it over the plate, and it runs over the drain board, which is tilted down at an angle over the web of textile material, in a uniform layer, to then fall from the lower edge of the drain board in a uniform film or veil on to the web, whose height of fall amounts to about 0-10 cm. That is the lower edge of the drain board takes up a position over the web that lies somewhere between nearly touching and being slightly above the web. The height must not be so great that the veil again loses uniformity in the fall and comes together to form individual concentrated threads of stream or strands.
When coating devices of this type are used, the quantities of liquid dye required for dyeing carpet are able to be quantitatively regulated with a high degree of accuracy and when they are applied to the fabric web running past under the drain board. However, to ensure a level application, the lower edge of the drain board must be especially uniform and the drain board must be particularly even. Even irregularities, such as a ground down rivet head or a welding spot, can already cause disturbances in the uniform run-off of the liquid, giving rise to inhomogeneities in the falling liquid veil and thus to visible streakiness in the final look of the dyed fabric.
In practice, it is not easy to optimally do justice to the important requirements. Carpet webs have a width of up to five meters and, therefore, the support for the run-off surface must cover the carpet web over this width without sagging, without vibrating during operation, and without showing any waviness or other disturbance, in particular in the lower edge of the run-off surface.
Up until now, one mostly manufactured the run-off surfaces out of sheet metal, connected them to the support, and then assembled them together with this support. Often enough, when the sensitive run-off surface experienced impacts when it was mounted on the support, which had to be quite heavy for reasons of stability, these impacts led to deformations, dents, etc. The runoff surface then had to be disassembled, which involved costly work, and be replaced by a new one, whereby in many cases even the support had to be completely removed. Also, a careful enough handling of the run-off surface during operation could not always be guaranteed, so that cumbersome replacements likewise had to be made. The same was true, for example, when the transition had to be made from a drain board with a straight edge to a drain board with a toothed or jagged edge, when the application called for a liquid dye with different physical properties.
The device underlying the introductory part of claim 1 can be inferred from the German Patent 28 12 219. In the case of the known device, the drain board consists of a baffle plate tilted downwards, whose lower edge section adjacent to the web is formed by a relatively thin, stretched foil, whose lower edge constitutes the run-off rim for the thin liquid film. The baffle plate, together with its thin foil, forms a plane, which is inclined in the requisite manner with respect to the horizontal plane.
From the German Patent 28 12 219, one cannot infer in detail how the foil is supposed to be tensioned. In any case, however, the flatness of the foil is supposed to be produced by the tensioning action, so that the foil must exhibit appropriate deformability, which makes the configuration highly sensitive in a mechanical respect.
The object of the invention is to create an operationally reliable device of this type, in which the run-off surface can be easily replaced.